The digital media

including text

image

graphics

audio and video etc.

has become a main way for information communication along with the popularization of Internet and the development of multimedia techniques. People can get almost information through the Internet. But this gives rise to serious problems including wide spread copyright violation

illegal copying

easy forging etc. How to provide copyright protection and implement covert communication has drawn extensive attention in recent years. As a main method for covert communication and copyright protection(watermarking)

information hiding has been widely studied and applied. In this paper

we make an introductory review on the information hiding techniques including the last achievement in this field. First

we give the general concepts and fundamental principles of information hiding such as the definition

characteristics

classification and general framework. Then

we analyze the processing model

the typical methods

the main application and the attack analysis of watermarking. Finally

we make a discussion on some open problems and point out possible directions for further research.